Military forces are confronted with chemical agents in battlefields and both military and civilians are at risk for chemical leaks and terrorist attacks using chemical weapons. Decontamination systems are important because they allow rapid neutralization of hazardous materials in the immediate area of a soldier. To date, decontamination systems include liquid solutions, solid sorbents, and gaseous mixtures that allow the rapid decontamination and restoration of materials and equipment in order to minimize downtime for military operations.
Several types of toxic chemical compounds are known to be useful as chemical warfare agents. These include mustard agents or gases known as blister agents, such as bis-(2-chloroethyl)sulfide, also know as HD, and nerve agents such pinacolyl methylphosphonofluoridate, which is also known as GD, and O-ethyl S-(2-diisopropylamino)ethylmethylphosphonothioate, which is known a VX. HD is a colorless, oily liquid that is highly insoluble in water and it is a powerful vesicant (causes blistering of skin) which affects the eyes and the lungs, blisters the skin, and is considered a carcinogen. HD is also cytotoxic to hematopoietic tissue and can be lethal at high doses. GD and VX are powerful nerve agents that attack the nerve cells and impair the functioning of the central nervous system.
As discussed in U.S. Pat. Nos. 6,245,957 and 6,723,891, to decontaminate the vesicant mustard gas and render it non-vesicant, it is necessary to oxidize the mustard gas to the corresponding sulfoxide. Nerve agents such as VX and GD are rendered non-toxic by perhydrolysis to their non-toxic phosphonic acids. The oxidation of HD to HD-sulfoxide (HDO) renders the gas non-vesicant. The reaction of a nerve agent with peroxide compounds is effective as an oxidation process to decontaminate nerve agents. Mildly-basic peroxide is also known to cause the perhydrolysis of VX and GD to their non-toxic phosphonic acids. Peroxides are desirable reactants for decontamination because they are non-toxic and non-corrosive, as compared to hypochlorite-based processes, which are toxic and therefore environmentally damaging.
Current hydrogen peroxide based decontaminants such as DF200® produced by Envirofoam Technologies and Decon Green® produced by Steris Corp require non-liquid activators and/or surfactants which leave a white solid residue following decontamination operations. This white solid residue has to be removed by rinsing of the decontaminated items. This is especially important for military vehicles so that they may maintain their low visibility and/or low IR signature.
Recently, a gaseous decontaminant, known as Modified Vaporized Hydrogen Peroxide (mVHP®) produced by Steris Corp., has shown that hydrogen peroxide (H2O2) vapor, when mixed with minor amounts of ammonia gas (NH3), is efficacious for the decontamination of chemical warfare agents and biological warfare agents such as anthrax on surfaces. Being that mVHP® is a gas, it is best suited to operate as a decontaminating “fumigant” for enclosed areas, such as buildings, vehicles, and aircraft interiors. An advantage of the mVHP® gas, is that when used for decontaminating chemical warfare agents and biological warfare agents, it does not leave a residue and is benign to sensitive equipment and materials. The mVHP® process is described in U.S. Pat. No. 7,102,052.
Although gaseous, NH3 is able to afford suitable activation of the H2O2 in the gas phase for the decontamination of chemical warfare agents VX and GD. However, gaseous NH3 alone would not be effective as an activator for a solution of H2O2 based decontaminants because of its inability to generate the necessary peroxo species required for facile HD oxidation. Peroxo species are typically generated by the reaction of H2O2 with alkali molybdates or bicarbonates in solution, to form peroxomolybdate or peroxocarbonate species, which are much more effective oxidation catalysis for HD than H2O2 itself. Such alkali activators are extremely stable for transport and storage. Their main drawback is the need to rinse away the white residues remaining following their use in decontaminating of chemical warfare agents VX and GD.
An alternate bicarbonate activator, ammonium bicarbonate (NH4HCO3) in powder form, would not leave a lasting residue as it decomposes to NH3, water, and carbon dioxide (CO2); a process greatly accelerated by heat. Thus, although NH4HCO3 could be utilized with H2O2 to generate a no-rinse, residue-free decontaminant, this material would not be stable under the potentially-uncontrolled storage conditions that are common to the military, such as in the field of combat.
Similar to the reasons discussed above, U.S. Pat. Nos. 6,245,957; 6,566,574; 6,723,890; and 7,390,432, also relate to the present invention. However, one significant distinction is that certain of the constituents are not stable and difficult to use in the field of combat.